The epidemiology of mesothelioma

Our plain-English summary of The epidemiology of mesothelioma, by M. Britton (Seminars in Oncology, 2002).

The study

• Author: M. Britton
• Journal: Seminars in Oncology
• Published: 2002;29(1):18-25
• Type of article: Review
• Cited by: 128 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

It has been more than 40 years since occupational crocidolite exposure in South African miners was found to be associated with development of malignant mesothelial tumors 30 to 40 years later. Similar cases were not seen in the amosite and chrysotile miners. Since then, epidemiological and toxicological knowledge have increased enormously, but mortality continues to rise steeply (5% to 10% per year) in most industrialized countries. Even with widespread asbestos abatement efforts, this increase is likely to continue in Western Europe and the United State well into the next century, at least until 2020. Unregulated use of asbestos in less industrialized countries may cause the epidemic to continue throughout the next century in those regions. Asbestos abatement seems to be successful as evidenced by a decline in the proportion of patients with peritoneal tumors, which are the most common malignancies in heavily exposed individuals. Whereas in the 1960s peritoneal tumors comprised up to 30% of the total, in recent years the proportion has fallen to about 10%, This changing ratio could also be due to the steady increase in pleural tumors. The difficulty in formulating the connection as to the etiology of mesothelioma resulted from an unforeseeable difference in the carcinogenicity of various asbestos and mineral fiber types and was compounded by the very long latency of the disease. Unfortunately, the use of a single term, "asbestos," to describe at least five fibrous silicate minerals, each with unique physical, chemical, and biological properties and not infrequently and naturally admixed, severely hampered scientific investigation into the occupational health risks. The field became confused and filled with debate. At the heart of the fiber type controversy lies a fundamentally differing view of the importance of biopersistence of various asbestos fibers in carcinogenesis. This review will deal with the epidemiology of mesothelioma with particular attention to the studies that elucidate the impact of various asbestos fiber types on the etiology of the disease.

Copyright 2002 by W.B. Saunders Company.

In plain English

This article was a narrative review by one author, drawing heavily on the work of Corbett McDonald. It surveyed case-control, cohort, lung tissue fiber, and Quebec chrysotile miner studies, plus British mortality projections. Six early case-control studies it reviewed reported relative risks of 2.3 to 7.0 for occupational asbestos exposure, with shipyard employment the most notable risk. A later 1980 North American study found the greatest relative risk for insulation work (46.0). The lung tissue studies consistently found no important difference in chrysotile between mesothelioma cases and controls. They did find higher amphibole levels, including tremolite, in cases. McDonald's summary counted 44 mesothelioma deaths among 11,538 deaths in chrysotile cohorts and 590 among 19,622 in amphibole-related cohorts. The author wrote that the data leave little doubt crocidolite carries a much higher risk than chrysotile, with amosite and tremolite probably in between. Peto and colleagues projected a peak of 2,700 to 3,300 annual male mesothelioma deaths in the United Kingdom around 2020. The author concluded that delay in action will leave rising mesothelioma rates for at least the next 20 years.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Narrative review of published epidemiological studies of mesothelioma, focusing on asbestos fiber type
• Who was studied: No new study population. The review covered published case-control studies, cohort mortality studies, lung tissue (lung burden) studies, the Quebec chrysotile miner studies and British mortality projections, relying heavily on McDonald's summaries.
• Exposure: Asbestos of different fiber types (crocidolite, amosite, chrysotile, tremolite, anthophyllite) in mining, manufacturing, shipyards, insulation and other trades. The review also discussed non-asbestos erionite fibers in Turkey.
• Main results:
  • In a series of six additional early case-control studies reviewed, all confirmed an association with occupational asbestos exposure. Relative risks ranged from 2.3 to 7.0, and shipyard employment was the most notable risk.
  • In a 1980 North American study by McDonald et al of 344 males, insulation work had by far the greatest relative risk (RR = 46.0). It was followed by asbestos product manufacture (6.1), heating trades (4.4), shipyards (2.8) and construction (2.6).
  • Across 43 cohort mortality studies summarized by McDonald, proportional mortality rates ranged from 2.5 to 102.3. The highest, 83.1 and 102.3, were in crocidolite-exposed workers in filter assembly and insulation work.
  • The controlled lung tissue studies reviewed (Table 2) consistently failed to show any important difference in chrysotile concentrations between mesothelioma cases and controls.
  • The same lung tissue studies found substantially higher concentrations of amphibole fibers, including tremolite, in mesothelioma cases than in controls.
  • In chrysotile cohorts summarized by McDonald, 44 of 11,538 deaths were from mesothelioma and 267 were excess lung cancers (proportional mortalities of 3.8 and 23.1 per thousand).
  • In amphibole-related cohorts, 590 of 19,622 deaths were from mesothelioma and 1,042 were excess lung cancers (proportional mortalities of 30.1 and 53.1 per thousand).
  • In the cohort of some 11,000 male Quebec chrysotile miners and millers, 38 mesothelioma cases were identified among more than 8,000 deaths before 1993.
  • In McDonald and McDonald's 1997 analysis of Thetford Mines workers, odds ratios for work in the central mines (higher tremolite exposure) were raised substantially and significantly for mesothelioma and lung cancer. In the peripheral mines (lower tremolite exposure) there was little or no evidence of increased risk.
  • Peritoneal tumors fell from up to 30% of mesothelioma cases in the 1960s to about 10% in recent years. The article states that peritoneal tumors had not become less common; instead, pleural tumors had steadily increased.
  • Peto et al predicted a peak of between 2,700 and 3,300 annual male mesothelioma deaths in the United Kingdom in about 2020.
  • The author wrote that the data leave little doubt that crocidolite carries a much higher risk than chrysotile, with amosite and tremolite probably in between.
• The authors' conclusion: The author concluded that knowledge has increased greatly, but that delay in action will result in rising mesothelioma rates for at least the next 20 years.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Crocidolite, Mesothelioma, Tremolite.

Medical terms in this study, explained in our Lexicon: Epidemiology, Mesothelioma, Crocidolite, Amosite, Chrysotile, Abatement, Etiology, Mineral Fiber.

Related studies

• The epidemiology of mesothelioma in historical context — J.C. McDonald, A.D. McDonald (1996)
• Epidemiology of malignant mesothelioma--an outline — J.C. McDonald (2010)
• Mesothelioma in Quebec chrysotile miners and millers: epidemiology and aetiology — A.D. McDonald, B.W. Case, et al. (1997)
• Veterinary cancer epidemiology — W. Misdorp (1996)
• Epidemiology of malignant mesothelioma in Australia — A.W. Musk, N.H. de Klerk (2004)
• Epidemiology of lung cancer: looking to the future — A.J. Alberg, M.V. Brock, et al. (2005)

Browse more research in Seminars in Oncology, or return to medical research.